Archive for category Tactile & Multimodal displays

Towards a Taxonomy of Vibro-Tactile Cues for Operational Missions, a poster presented by Nuphar Katzman

Abstract. The present study is aimed to serve as a preliminary stage in the examination and implementation of a taxonomy of vibro-tactile cues for operational missions. Previous researches showed that using the tactile modality can help increase soldiers’ performance in terms of response time, accuracy in navigation and communication under busy conditions and/or high workload. The experimental pilot reported here focuses on how users (infantry soldiers) perceive tactile cues in terms of implication and urgency during such missions. Fifteen reserve soldiers completed a navigation mission in a virtual environment. During the navigation they received random tactile cues and were asked to assess the suitability of each cue to a specific context. At the end of the session, participants filled a subjective questionnaire about their experience with the tactile cues. Results revealed three (out of five) superior cues, in terms of accurate identification and consistent association. This work provides the foundation to further develop a taxonomy of tactile cues for information types in operational missions. Future work should examine the identification of cues and their associated meanings when the relevant events occur in the simulation and outside in field tests.

Abstract: Cognitive control has been extensively studied using the auditory and visual modalities. In the current study, a tactile version of the Simon task was created in order to test control mechanisms in a modality that was less studied, to provide comparative and new information. A significant Simon effect – reaction time gap between congruent (i.e., stimulus and response in the same relative location) and incongruent (i.e., stimulus and response in opposite locations) stimuli – provided grounds to further examine both general and tactile-specific aspects of cognitive control in three experiments. By implementing a neutral condition and conducting sequential and distributional analysis, the present study: (a) supports two different independent mechanisms of cognitive control – reactive control and proactive control; (b) reveals facilitation and interference within the tactile Simon effect; and (c) proposes modality differences in activation and processing of the spatially driven stimulus-response association.

Method: Four experiments of tactile Simon task, preceded by an alerting signal (AS) in visual, auditory and two architectures of tactile.

Two types of tactile signals were developed for this task. All stimuli were displayed on the participant’s back.

Background: Alerts in the cockpit must be robust, difficult to ignore and easily recognized. Tactile alerts can provide means to direct the pilot’s attention in the already visual-auditory overloaded cockpit environment. Objective: This research examined the thigh as a placement for vibrotactile display in the cockpit. Here we: a) report initial findings concerning the loci and properties of the display, b) evaluate the added value of tactile cueing with respect to the existing audio-visual alerting system, and c) address the issue of tactile orienting; whether the cue should display ‘flight’ or ‘fight’ orienting. The tactor display prototype was developed by a joint venture of Israel Aerospace Industries (IAI), Lahav division and the Ben Gurion University of the Negev (patent pending 11/968,405). Methods: Vibrotactile display mounted on the thigh provided directional cues in the vertical plane. Two vibrotactile display modes (eight and four tactors) and two response modes (compatible, i.e. flight (away from hazard) and inverse, i.e. fight (toward hazard)) were evaluated. Results: Vertical directional orienting can be achieved by a vibrotactile display assembled on the thigh. Four tactors display mode and the compatible response mode produced more accurate results. Conclusion: Tactile cues can provide directional orienting in the vertical plane. The benefit of adding compatible tactile cues with the visual and auditory cues alone has yet to be reinforced. Nevertheless, flight mode, i.e. directing towards escape from hazardous situations, was preferred. Application: Potential applications include providing directional collision alerts within the vertical plane, assisting pilot’s elevation control, or navigation.

The Thermal Grill Illusion was first described by Thunberg (1894) and later replicated by others (Craig & Bushnell, 1994) as the sensation of paradoxical strong or painful heat elicited by touching interlaced mildly warm and cool stimuli of 20°C and 40°C respectively. Green (2002) has introduced the sensation of non-painful heat elicited by similar grill apparatus of smaller temperature range (warm 35°C-40°C and cold ≥27°C).

Our aim is to generate thermal grill illusion (TGI) stimuli for a tactile display. The majority of tactile interfaces used today are based on vibration and pressure. No previous references shows the use of thermal displays as a stand-alone signal source, nor is there evidence of the use of the thermal grill illusion for that purpose.

This is the first use of Thermoelectric Coolers (TEC) technology for generating a thermal grill stimuli based display. We have developed a prototype which consists of three thermal actuating units (TAU) in contact with the glabrous skin of the arm. Direct and separate computer control allows for defining the temperature and the signal duration of each of the TAUs. This architecture enables us to define the optimal characteristic for TGI signals and to explore the possibilities of tactile stimuli within the sub-modality of thermal perception.

The TAU is composed of several components yet its core is the TEC (as shown in the two images below). The TTD consists of three TAUs. In the first prototype of the TTD, each TAU was mounted on a velcro belt. In the New prototype all three TAUs are mounted on a Silicon based casing and thus wearing the display is easier. Various TGI stimuli configurations. Interlacing Hot (H) and Cold (C) Stimuli can generate various combinations.

TAU components

An assembled TAU

TTD – schematic presentation of the P/T

TTD – old configuration

TTD New Mounting

TTD New P/T

TGI stimuli configurations

The TTD was developed with my graduate student Yael Salzer. The second P/T was improved by the work of two wonderful students Or Ben-David and Yossi Falkovitch.

Three experiments examined the use of vibrotactile cues to guide an operator toward a target. Vibrotactile stimulation on the hand can provide spatially stabilizing cues for feedback of subtle changes in position. When such feedback is present, a deviation from the point of origin results in tactile stimulation indicating the direction and magnitude of the positional error. Likewise, spatial deviation from a desired position displayed tactually can provide robust position guidance and stabilization sufficient to improve the acquisition time and accuracy of fine cursor control. A major advantage of this mode of information representation is that it can be present at the same time as visual cues with minimal cross-modal interference. Our findings suggest that performance is actually enhanced when both tactile and visual cues are present. Although previous studies have suggested that various forms of tactile feedback can provide position guidance and stabilization, to our knowledge, this work is the first that details the effect of tactile feedback on target acquisition directly.

Here are some more detail about the experiments and some images:

•Experiment 1 – focued on where to place the tactors – tactor placements on the palm versus on the back of the hand, while targets appeared to the left and right.

•Experiment 3 – focused on the effectiveness of the tactile cues, do they facilitate the entire movement of just the initial movement toeard the target and the fine tuning on target – investigate the interaction between the near-target pulse rate and on-target cues and establish if there are performance differences between discrete and continuous distance information for target selection.